It's 1922 and Jack Haldean, crime writer and ex-wartime pilot, is enjoying the local fete on a beautiful summer's day in Sussex. It's idyllic - the sort of idyll he dreamed of during the war. However, that idyll comes to an abrupt end when Jack's former fellow officer, Jeremy Boscombe, is found murdered in the fortune-teller's tent. Jack soon realizes that the roots of the crime go back to the battle of the Somme. But how? And what are the dark secrets in the tunnels under the battlefield?